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      <title>Redis 分布式锁过期了，还没处理完怎么办？ - 交互式测验</title>
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    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>Redis 分布式锁过期了，还没处理完怎么办？ - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
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                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
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                    <div id="hint-container" class="hint-container"></div>
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      <script>
        const quizData = [
  {
    "question": "根据文档，当使用 Redis 实现分布式锁时，如果任务执行时间超过了锁的过期时间，最直接的后果是什么？",
    "options": [
      "Redis 服务器会因超时而崩溃。",
      "该任务会被 Redis 自动标记为失败。",
      "锁被自动释放，可能导致其他线程/进程获取锁，从而引发并发问题。",
      "锁的过期时间会自动延长一倍。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档开篇就指出了核心问题：如果锁的过期时间到达而任务未完成，锁会被自动释放。这打破了锁的互斥性，其他进程或线程可能会获得这个本不该被释放的锁，进入临界区执行代码，从而导致并发执行和潜在的数据不一致问题。",
    "source": "文档引言部分（第一段）",
    "hint": "思考一下分布式锁最根本的目的是什么？当锁提前失效时，这个目的还能达到吗？"
  },
  {
    "question": "文档中提到的 Redisson 框架（如 RLock）为解决锁提前过期问题提供了什么便捷的机制？",
    "options": [
      "它会预先估算任务执行时间，并设置一个绝对安全的超长过期时间。",
      "它提供了一种“看门狗”（Watchdog）机制，能够自动为即将过期的锁续期。",
      "它强制所有任务必须在锁的初始过期时间内完成。",
      "它在锁过期后，会自动回滚任务已做的操作。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，像 Redisson 这样的分布式锁库提供了锁的可续约机制。Redisson 的 RLock.lock() 方法在底层实现了一个“看门狗”（Watchdog）机制，它会启动一个后台线程，在锁的过期时间到达前，如果客户端还持有锁，就会自动延长锁的过期时间，从而避免了手动管理的复杂性。",
    "source": "文档中「2. 使用分布式锁的可续约机制」部分",
    "hint": "文档提到了一个流行的分布式锁库，它通过一个“自动”功能来简化锁的生命周期管理。"
  },
  {
    "question": "为了从根本上防止因锁过期导致任务重复执行而产生的数据不一致问题，文档推荐了哪种设计原则？",
    "options": [
      "任务降级（Task Degradation）",
      "服务熔断（Circuit Breaking）",
      "任务幂等性（Idempotency）",
      "读写分离（Read-Write Splitting）"
    ],
    "correctAnswerIndex": 2,
    "explanation": "幂等性是指一个操作执行一次和执行多次所产生的影响是相同的。文档指出，通过将任务逻辑设计为幂等操作，即使锁过期导致任务被重复执行，也不会产生错误的结果或数据不一致。这是一种非常重要的防御性编程策略。",
    "source": "文档中「5. 确保任务的幂等性」部分",
    "hint": "思考一个数学概念：哪个特性保证了 `f(f(x)) = f(x)`？"
  },
  {
    "question": "在不使用 Redisson 这类高级库的情况下，如果我们想自己实现锁的续期，文档提到的一个可行方法是？",
    "options": [
      "在任务开始前，一次性将锁的过期时间设置为永久。",
      "依赖 Redis 的持久化机制（如AOF）来恢复锁。",
      "在任务执行代码中，启动一个独立的定时任务，周期性地检查并使用 EXPIRE 命令延长锁的有效期。",
      "修改 Redis 服务器的源代码，改变过期策略。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在「1. 延长锁的过期时间」和「4. 实现锁的自动续期」部分都提到了主动延长锁有效期的策略。一个具体的实现方式就是通过一个定时任务（或在主任务流程中嵌入计时逻辑），定期地对持有的锁的 key 执行 EXPIRE 或 PEXPIRE 命令，重置其过期时间，以确保在任务完成前锁不会失效。",
    "source": "文档中「1. 延长锁的过期时间」与「4. 实现锁的自动续期」部分",
    "hint": "如果不想让一个东西“到期”，最直接的办法就是在它到期前不断地“推迟”它的到期日。"
  },
  {
    "question": "根据文档中的代码示例和“合理的锁释放机制”，释放锁的操作（如 `redisClient.del(lockKey)` 或 `lock.unlock()`）通常应该放在哪个代码块中？",
    "options": [
      "try 块的末尾，任务逻辑成功执行后。",
      "if (acquireLock) 块的外部。",
      "catch 块中，仅在发生异常时执行。",
      "finally 块中，以确保无论任务成功还是失败，锁都能被释放。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "为了防止死锁，释放锁的操作必须得到保证执行。将释放锁的逻辑放在 `finally` 块中，可以确保无论 `try` 块中的业务逻辑是正常执行完毕，还是因为异常而中断，释放锁的操作最终都会被执行。这是一种健壮的编程实践。",
    "source": "文档中「1. 延长锁的过期时间」的代码示例和「6. 设计合理的锁释放机制」的理念",
    "hint": "在 Java 或类似语言中，哪个代码结构被设计用来确保资源（如文件、连接、锁）总是能被清理？"
  },
  {
    "question": "在设置分布式锁的初始过期时间时，文档建议了一种基础但重要的策略是什么？",
    "options": [
      "总是使用默认的30秒过期时间。",
      "将过期时间设置为尽可能短，以提高并发性能。",
      "通过性能分析估算任务的最大处理时间，并设置一个足够长的合理过期时间。",
      "让客户端在获取锁时随机选择一个过期时间。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档的第三点指出，一个基础的策略是合理评估任务的执行时间。通过对任务进行性能测试和分析，了解其在各种负载下的最大可能执行时间，然后设置一个比这个最大值更长的、带有安全边际的过期时间。这虽然不能完全杜绝问题，但是一个简单有效的第一道防线。",
    "source": "文档中「3. 使用合适的过期时间」部分",
    "hint": "在采取复杂的续期方案之前，最简单直接的避免锁提前过期的方法是什么？"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
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        let score = 0;
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          optionsListEl.innerHTML = '';
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            return;
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            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
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            nextBtn.style.display = 'block';
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            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
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                // 高亮正确答案
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                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
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            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

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            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
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        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  